Charles e



(Nd Model.)

- l c. E. SCRIB1\IER MULTIPLE SWTCHBOARD SYSTEM.

N0503,'099.. Patented'Aug. 8, 1893.

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN C ELECTRIC COMPANY, OE SAME PLACE.

' M u LTI PLE-SWITCH BOARD SYSTEM.

SPECIFICATION'formng partv of Letters Patent No. 503,099, dated August 8, 1893.

Y Application tiled October 13, 1891. Serial No. 408,585. (No model.)

My invention relates to multiple switchV board systems for telephone exchanges, and

its objects are to provide means whereby the individual annunciator of a telephone line-is x rendered inoperative when a connection is made to the line Without the interpolation of contacts in the line circuit, and to provide a suitable means for testing at one section of switch board, to determine whether any teleL zo phone line is in use at another board.

My invention comprises, first, telephone lines extending from a substation and permanently connected together through an annunciator and retardation coil and connected each z5 to the corresponding line spring of several spring jacks, the frames of the spring jacks being insulated from the line springs and electrically connected together, and to such a point of one of the lines as to short circuit the annunciator when a connection is established between the line springs of one of the jacks andthe frame of its jack; and connecting plugs having two contacts one'adapted to engage with one of the line springs and the other to make contact with the other of the line springs and theframe ofthe jack, whereby the individual annunciator of the line is short circnited when the connecting plug is inserted into a spring jack of its line; and 4o second, included between the two contacts of a connecting plug, a battery and an electro magnetic signaling device, whereby a signal is given by the signaling device when the two contacts of the connecting plug are short circuited, and means whereby the two contacts of thefvplugshall be short circuited when the plug is inserted into a spring jack of the line already in. use.

My invention will be more readily under- 5o stood by reference to the accompanying drawing which is illustrative thereof.

In the drawing I have shown two substations l and 2 connected to their respective spring jacks on two sections of multiple switch board and to their individual annunciators and retardation coils; at each of the switch boards I have shown connecting plugs of the character necessary in carrying out my invention, calling keys and a special three positionkey, adapted, when inone of its posi- 6o tions, to connect the operators telephone in a branch circuit between the contactsof the connecting plugs; in another position to disconnect the operators telephone from the plug circuit; and in the third position to connect thetesting battery and signaling device to the two contacts ot'one of the connecting plugs.

The lines from station 1 I have shown as completing a metallic'circuit. The circuit 7o may be traced over line a, through annuncialtor a* and retardation coil a2 to line a?, and

thence returning to stationl l. Thecorre- .sponding line springs of spring jacks a4 a5 andy of answering jack a.'7 are connected to the 75 line a and the re'mainingline springs are connected to the line a3. The insulated frames of spring jacks a4 c5 anda,7 are electrically connected together by the wire a6 and are connected to the line circuit at a point inter- 8o mediate between the individual annunciator a' and the retardation coil c2. The circuit from station 2 is shown as grounded and may be traced over line b through annunciator b',

retardation coil b2, returning over line wire b3, through-resistance bs and earth to station 2. The lines b and b3 are similarly connected to the line springs of spring jacks b4 b5 and answering jack la7, and the frames of the spring jacks b4 b5 197 are connected together 9o by the wire be to the line circuit between the individual annunciator b and the retardation coil b2. One of the line springs of each of the spring jacks is made shorter than the other and is adapted to come into contact with a different portionof the connecting plug. A connecting plug c is shown in section at the first board, at the left of the drawing. yIt consists of a core c terminating in a spherical tip which is adapted to come into contact with roo f the shorter line spring of the spring jack. Surrounding the central core and insulated from it is the metallic sleeve c2, of such diameter and length as to come into contact with both the longer line spring and the frame of the jack into which it is thrust. The connecting plugs d CZ, shown as part of the operators outt at the second board, are of similar construction. Their tips are electrically connected through flexible cords and a condenser e; their sleeves are connected directly. Two calling keys f. g are included one on either side of the condenser e in a circuit connecting'the two plugs. These calling keys are of the ordinary construction and operation; either of them serves, when depressed, to disconnect the terminals of one of the connecting plugs from the other connecting plug and to connect them to the two poles of a calling generator.

Branch connections are extended from the wires joining the corresponding contacts of the connecting plugs to a listening key h. This key consists of a cam t', preferably of insulating material, pivoted at 2", and having attached to it a handle i2 projecting above the keyboard. At each side of the cam are two springs lc 7c Z l normally separated, but so disposed with relation to the cam t' that when the handle 2 is pressed in one direction the two extensions of the cam t' engage with the curved extremities of the springs Z Z and force them into contact with springs 7o c; the springs Z Z' are connected to the circuits joining the corresponding parts of the two connecting plugs d cl; the two springs k k are connected to the two terminals of the 0perators telephone set m; hence when the key is in one of its positions the telephone set m is in a branch connection between the tip and the sleeve of the connecting plugs, orbetween the two sides of the circuit of two subscribers in communication. Two contacts n n are so disposed as to be normally separated from the springs lc 7o'. These springs are given an inward pressure against the cam t' but bear against the faces of the cam when it is in its normal position, that is, when the handle i2 stands vertically, but when the cam is thrown to the left the springs 7c Tc are allowed to close in upon the contacts 'n n. The spring n n are connected through the low resistance coil of a sounder o and the test battery p. Thus when the key h is thrown into its eXtreme left position the springs 7c k close upon the contacts n n and connect the test battery and its sounder to the tip and sleeve of the test plug CZ. A clearing out annunciator q is in a branch connection between the wires joining the corresponding contacts of the plugs d d.

Having thus described the apparatus employed in my invention I will nowproceed to describe the various operations involved in cstablishin g communication between two subscribers. Suppose, for example, that subscriber at station l desires to communicate with subscriber at station 2. The operation of the calling generator at station l causes the shutter of annunciator c to fall; the operator perceiving this,inserts one of her plugs, as plug d, into the answering jack a7 of line from station 1. The tip of plugclcomes into contact with the shorter line springrof the answering jack al while the sleeve makes contact with both the longer line spring s and the frame t ot the spring jack, whereby the annunciator a is short circuitcd, since any current entering over line ct will find circuit through the line spring s, through the sleeve of plug d, to the frame t of the spring jack, and thence through the retardation coil a2 to line a3. She now throws the cam of listening key h into its right position, whereby the circuit from station 1 is extended to her telephone set m and she is enabled t-o communicate with the subscriber. Having learned the number of the station desired, the operator proceeds to test to determine whether the line called for is already in use or not. To make this test she throws the key h into its left position, whereby the batteryp and the sounder o are connected to the contacts of plug d. As she inserts the plug into the jack both the tip and the sleeve come into contact with the frameu of the jack b4, thus momentarily short circuiting the batteryp through the soundero, contacts n Z', sleeve of plug al', frame u, tip of plug d', thence returning to contacts 7c and n, and the sounder o gives a signal which, however, theoperator ignores. Inserting the plug still farther into the spring jack, the tip ot plug d comes into contact with the longer line springt; of jack b4 and the circuit is completed from the tip of plug d', through the annunciator b', returning to frame u of springjack b, but the battery p is too feeble to operate the sounder o through the resistance of annunciator b', and the sounder does not respond. This indicates to the operator that the line of station 2 is not in use. Inserting the plug d still farther into the jack the tip comes into contact with the shorter spring w, While the sleeve is in contact with both the longer spring 'v and the frame u, whereby the annunciator b of line from station 2 is short circuited in the same manner as was described ot' a when the plug d was inserted into the answering jack a7. Hence to a current arriving from either station l or station 2 both annunciators a and b would be inoperative. Suppose now that an operator at the iirst board should test the spring jack b5 with similar apparatus; the plug at this board is shown in the position for making such a test at spring jack 0,4 instead of b5. As she thrusts her testing plug cl2 into the jack b5 her battery e would be momentarily short circuited through the tip of the plug and frame of the jack to the sleeve of the plug, and her sounder will givea response. As she thrusts the plug still farther into the jack and the tip comes in contact with the longer line spring c her battery will again be short circuited through the tip of her testing plug cl2, through the line spring fu', thence to the line IOO spring 'u of jack h4, through the sleeve of l plug d to the frame to of jack b4, thence returning to the frame u of jack b5, thence to the sleeve of her testing plug d2, and her sounder will give a second response. Thus two signals from the responsive device indicate to an operator testing a line that the line tested is already in use. Having made the test and found the line notbusy the operator allows the key h to resume its normal position. The subscribers at stations l and 2 are now in communication, through a circuit which contains no contacts save those of the plugs with the spring jacks and those in the ringing keysf and g. It will be noted that the line wires a and a3 are still connected together through the retardation coil a2, but on account of the very great self induction of this coil an inappreciable portion only of the telephonie currents will be shunted through the coil. This explanation applies also to .the lines b and b5. When the subscribers have completed their communication either or both send a generator signal for disconnection; this current finds cfircuit through the clearing out annunciator q which is operated and notities the operator that the lines may be disconnected.

It is obvious that any other form of signaling device might be employed in connection with the test battery p to replace the sounder 0 and also that many other forms of switch might be used to perform the functions of key h. These, however, do not form an essential feature of my invention.

l-Iaving thus described my invention, I claim as new and desire to secure by Letters Patent- 1. The combination ot the spring jack having two line springs of different lengths and a frame insulated from the line springs with a plug having two contact pieces, one adapted to make contact with one of the line springs, and the other to make contact with both the other line spring and the frame of the jack, substantially in the manner and for the purpose specied.

2. In combination telephone lines extending from a substation, connected together through a retardation coil and an annunciator and connected one line wire to corresponding line springs of several spring jacks, and the other line wire to the remaining line springs of the same spring jacks, a plug provided with two contact pieces one of which is adapted to make contact with one of the line springs of a jack, and the other to make contact with both the other line spring and the frame of the jack, and a connection extending from the frames of thejacks to apoint of the branch connection joining the two lines intermediate between the retardation coil and the annunciator, whereby the annunciator is short circuited when the plug is thrust into a jack,substantiallyin the manner and for the purpose specified. v

3. In combination two connecting plugs each having two Contact pieces, corresponding contact pieces being electrically connected one pair directly and the other pair through a condenser, keys adapted to disconnect both contact pieces of either plug from the corresponding contact pieces of the other and to connect them to the poles of a calling gener: ator, an annunciator in a branch circuit between the two contact pieces of the plugs, a key capable of being placed in three positions, and provided with contacts adapted when in one of its positions to connect the telephone set in a branch circuit between the two pairs of corresponding contact pieces, and when in another position to connect the test battery and a low resistance electro magnetic signaling device in a similar branch circuit, and when in its intermediate position to disconnect both the telephone set and battery and sounder from the pairs of corresponding contact pieces, substantially in the manner and for the purpose specified.

4. In combination telephone lines extending from two substations, each pair of line wires being connected one to similar line springs of several spring jacks and the other to the remainin g line springs of the same spring jacks, and being connected together through a retardation coil and an annunciator, and having a branch circuit extending from a point intermediate between the annunciator and the retardation coil to the frames of the several spring jacks of its own line, two connecting plugs one in a springjack of each of the telephone lines, each plug being provided with two contacts, one of which engages with one of the line springs of the jack into which it is thrust, and the other of which engages with both the other line spring and the frame of the same jack, whereby ashort circuit is completed around the annunciator of that line, conductors connecting corresponding contact pieces of the two plugs and a clearing out annunciator in a branch circuit between the conductors, substantially in the manner and for the purpose specified.

5. In combination telephonelines extending from two substations, each pair of line wires being connected one to similar line springs of several spring jacks, and the other to the remaining line springs of the same spring jacks, and being connected together through a retardation coil and an annunciator, and having a branch circuit extending from a point intermediate between the annunciator and the retardation coil to the frames of the several spring jacks of its own line, two connecting plugs one in a spring jack of each of the telephone lines, each plug being provided with two contacts, one of which engages with one of the line springs of the jack into which it is thrust, and the other of which engages with both the other line spring and the frame of the same jack, whereby a short circuit is completed around the annunciator ofv` that line, conductors connecting corresponding contact pieces of the two plugs, a ktest battery IOO IIO

and an electro magnetic signaling device in the branch circuit between the two conductors joining the corresponding contact pieces ot' the loop plugs, and a key adapted to disconnect the branch circuit containing the signaling device and the test battery from the conductors, substantially in the manner and for the purpose specified.

G. In a testeircuit for multi pleswitch boards, in combination,a spring jack furnished with a line spring and a frame insulated therefrom, a plug provided with a contact piece, making contact with both the line spring and the frame of the jack, a second spring jack having a similar line spring electrically connected to the line spring of the first spring jack and a frame electrically connected to the frame of the iirst spring jack, a loop plug having two contact pieces, one of which makes contact with the line spring and the other with the frame of the second spring jack, and a test battery and an elect-ro magnetic signaling dcvice included in abranch circuit between the two contact pieces of the second plug, substantially as and for the purpose specified.

7. The combination, with a metallic circuit telephone line extending from a substation to a central station, ot' line terminals at the central station each having twocontact pieces connected to the different sides of the line respectively, an electric indicator and a retardation coil included in a bridge between the two sides of the line, and contact pieces adapted to short circuit the electric indicator when a connection is made to one of the line terminals, substantially as specified.

In witness whereof I hereunto subscribe my name this 14th day of September, A. D. 1891.

CHARLES E. SCRIBNER.

Titnessesz FRANK R. MCBERTY, GEORGE L. CRAGG. 

